[R-390] Broadcast Band On Other Bands

[Scott, Barry (Clyde B)]

I'm guilty of spraying the wafer-style bandswitch with DeOxit.  It was before I knew that was a bad thing to do.  I wonder if this is phenomenon is a result of this?  Perhaps the bandswitch properties are changing as the set gets warmer or sits on the same frequency for an extended time.

Barry(III) - N4BUQ


> From: blw [mailto:ba.williams@charter.net]
> 
> Yes, mine is a 56 Motorola and you described the effect 
> better. It is a
> sudden gain without noise or harmonics. I have not had the IF 
> 
> Barry
> 
> > Mine does the same thing.  It's almost like it gets a 
> sudden 10dB gain.  Is
> > yours a '56 Motorola?  I wonder if it's 
> manufacturer/contract specific.
> > 
> > Barry(III) - N4BUQ

I think we're onto a trend.  My '54 Motorola does it too, on 4-7.
In CAL, the carrier meter reads 10-20dB lower than on the
other bands.  I can clear it by briefly! shorting the middle
RF coil's trimmer to ground.  Days go by, then it's back down.
I'm not saying it's the trimmer (the short is just a convenient
way of generating a lot of EM racket), but that's where I'll look
first.  IIRC it doesn't get detuned, just loses gain.  I suspect
loss of Q due to a high-resistance contact.  Now that I have
a nice signal generator, I'll take some stage gain readings
while it's bad, then clear it and repeat.
<snip>

73,
Dave Wise